Mode of operation
A block cipher mode of operation is a method for applying a block cipher to messages consisting of one or more blocks.
Software Security for Developers
A mode of operation defines how a block cipher processes messages longer than a single block and may provide additional security properties.
- How it is used
- Explains how AES handles messages longer than one block and guides developers toward secure encryption modes.
- How deep it goes
- Defines block processing, demonstrates ECB leakage, explains CBC chaining and IVs, and recommends GCM without mathematical proofs.
- Examples
- Uses a 1,605-byte message, repeated HTTP responses, ECB block diagrams, CBC chaining, and AES-GCM authentication tags.
- What you can do after
- Configure AES encryption with a nonreused random IV and choose GCM when confidentiality, integrity, and authenticity are required.
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Real-World Cryptography
A mode of operation is a method for applying a block cipher repeatedly to data blocks to encrypt messages of varying length.
- How it is used
- Explains how to encrypt messages longer than one block while exposing why naive independent encryption leaks patterns.
- How deep it goes
- Defines padding, ECB, and CBC with short operational explanations, but stops short of detailed mode internals.
- Examples
- Uses a 16-byte AES block, an eight-byte padding illustration, and the recognizable ECB penguin image.
- What you can do after
- Evaluate how padding and mode selection affect long-message encryption and recognize ECB pattern leakage.
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Related concepts
- cipher block chaining modeincludes · Cipher block chaining is a block-cipher mode that XORs each plaintext block with the preceding ciphertext block before encryption, using an initialization vector for the first block.
- electronic codebook modeincludes · Electronic Codebook mode is a block-cipher mode that encrypts each plaintext block independently with the same key.
- Galois/Counter Modeincludes · Galois/Counter Mode is an authenticated-encryption mode that combines counter-mode encryption with authentication of ciphertext and associated data.
- AESused by · AES is a standardized symmetric block cipher that encrypts and decrypts data in 128-bit blocks using 128-, 192-, or 256-bit keys.
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